Commonalities 8.0.0 alignment and fix validation warnings

[GillesInnov35]

Problem description
Commonalities 8.0.0 alignment - https://lf-camaraproject.atlassian.net/wiki/spaces/CAM/pages/789086209/Analysis+of+Commonalities+0.8.0

Expected behavior

Artifacts directory restructured for $ref consumption camaraproject/Commonalities#606

Testing artifacts for 400 Syntax Error including empty request body scenario camaraproject/Commonalities#618

Clarification on string `maxLength' value camaraproject/Commonalities#620

Added rule for undeclared properties in request bodies camaraproject/Commonalities#634

Added mandatory info.description templates to common artifacts and samples camaraproject/Commonalities#635